Although there is nothing concrete, we cannot say that no evidence exists. Interpretations of past historical events could actually be correct, however we can not ever prove anything from ancient history conclusively.

Logic seems to dictate that since we are seeing so many reports regarding aliens over the past 50 years- along with endless photographs in which many were taken before the advent of CGI- that the same process may also have occurred throughout history.

If we can accept that any of the photographs (even just one) over the past 50 years demonstrates proof of the existence of aliens, then it is highly probable that someone in ancient history may also have recorded such an experience, and we just have not discovered it yet.

We must also contend with the probability that peoples of ancient times would have absolutely no concept whatsoever of the existence of other worlds, solar systems, galaxies et al, and therefore would have reference point nor speculative ideas of what they were actually looking at if they had seen any strange craft or alien humanoids. Therefore, they would not be able to accurately describe what they were seeing in terms that would make any sense to us in modern times.

How can anyone become an atheist when we are all born with no beliefs in the first place? We are atheists because we were born this way.

Or... we can say the same explanation for aliens today is the same for yesterday. People see things in the sky they can't explain (it's why most reports of ufo's come from average joes and not astronomers).

People have waking dreams, or hallucinations, or delusions, just like they do today. And whereas today they explain it with the current popular idea of aliens (which various people have shown to have been a culturally evolved phenomena) times past it was demons like succubi or fairies or other myths.